Final answer:
Beriberi is caused by a deficiency of thiamine (vitamin B1). It was prevalent in East Asia due to diets high in polished white rice. Symptoms include appetite loss, nervous system disorders, and cardiovascular issues.
Step-by-step explanation:
Beriberi is a disease caused by a deficiency of thiamine, also known as vitamin B₁. Historical evidence from East Asia suggested that beriberi was prevalent among those who consumed a diet primarily consisting of polished white rice, which lacked thiamine. Dr. Takaki Kanehiro's observations in the Imperial Japanese Navy led to the belief that diet was the cause of beriberi, although he incorrectly attributed the prevention of the disease to protein. The breakthrough came when Christiaan Eijkman discovered the importance of unpolished rice in preventing beriberi in chickens, leading to the recognition of what Frederick Hopkins termed "accessory factors"—vitamins necessary for bodily function.
The deficiency of thiamine can lead to a range of symptoms including appetite loss, nervous system defects, edema, cardiovascular changes, and gastro-intestinal disorders. There are two main forms of the disease: Dry Beriberi, characterized predominantly by nervous symptoms, and Wet Beriberi, associated with edema and serous effusions.